Most of images shot with digital cameras and image devices of camera-embedded mobile phones which have been spread recently are produced in formats based on an image file format standard for digital still cameras (hereinafter, referred to as Exif (a registered trademark) (EXchangeable Image File format)) (for example, disclosed in Patent Literature 1).
Image files in the Exif format include camera information and thumbnail image data as well as main image data. Compared to main image data in a high density of pixels, thumbnail image data with a small data size can be processed at high speed. Thus, it is possible to speedily display a list of images by use of thumbnail mages included in image files in the Exif format.
However, thumbnail images are defined in an aspect ratio “4:3” and defined by an image size “160×120” in comparison with main images which may include vertical images and horizontal images as well as images having various aspect ratios (aspect ratios) in image files in the Exif format. Thumbnail images store main images which are reduced in size but with maintaining their aspect ratios. Thus, blanks may be formed in displayed parts when an image list is produced using thumbnail images included in image files in the Exif format.
This drawback will be described in detail with reference to FIG. 9. FIG. 9 shows an example of a main image 501 which is a vertical image described in an image file in the Exif format. In an image file in the Exif format, a thumbnail image, which is a horizontal image with an aspect ratio “4:3”, does not match with a vertical image. Therefore, as shown in FIG. 9, blanks (illustrated using slashes) should be formed in the left and right areas around a thumbnail image 502 corresponding to the main image 501 which is a vertical image described in an image file in the Exif format.
FIG. 10 shows an example of a main image 601 which is a horizontal image with a wider aspect ratio (e.g. an aspect ratio “16:9”) than an aspect ratio “4:3” in an image file in the Exif format. In an image file in the Exif format, a thumbnail image having the aspect ratio “4:3” does not match with an image having the aspect ratio “16:9”. Therefore, as shown in FIG. 10, blanks should be formed in the upper and lower areas around a thumbnail image 602 corresponding to the main image 601 with the aspect ratio “16:9” in an image file in the Exif format.
Considering an image list which is produced using thumbnail images described in image files in the Exif format, it is possible to display a list using thumbnail images precluding blanks. However, as shown in FIG. 11, a list of thumbnail images precluding blanks includes mixture of images having various aspect ratios; this may cause a disorder in displayed content while degrading visibility.
In particular, mobile phones using images in various applications, such as applications for displaying standby screens or icons, may suffer from a large number of images having different sizes and different aspect ratios in comparison with generally-available digital cameras. Therefore, an image list using thumbnail images may describe mixture of images having different sizes so as to undergo degradation of visibility.
Additionally, Patent Literatures 2 and 3 disclose display devices which are designed to display square-shaped images in an image list, thus improving visibility of images. Thus, it is possible to improve visibility by displaying square-shaped images in an image list.